If it was Europe I imagine it would be easy to tell
This would be an excellent question for /r/AskAnthropology. Cultural anthropology is my specialty, and my experience with archaeology is limited to a couple classes and some fieldwork, but my fieldwork might give some insight here.
We were digging in a floodplain by a river. The site had been magnetically imaged, so we had a good idea of the layout of the occupations that had been in this area and knew where to dig. The site would open every summer, and they'd unearth and record a different section each year, then re-bury it.
This particular site had access to good stone, the river, and fertile land due to the proximity to the river. Excavations revealed settlements as old as 10,000 years- this was a site that had been occupied by different groups since the ice age.
If I recall, I think there were at least 4 or 5 different groups that had occupied this same prime real estate, separated by hundreds of years, over the course of the past ten thousand. I was helping to excavate the palisade wall, a wall of vertical posts varying between 4 and 7 inches in diameter, between which material was woven to create a perimeter wall around the village, which was about the size of a football field. We came across a bunch of stuff we didn't quite understand at first- stonework and other items at depths we didn't expect, and even a haphazard human burial at an unusual depth.
Long story short, the new settlers on the land, while digging their trench for this wall, accidentally came across an earlier human burial. They dug even deeper and reburied the bones. They necessarily must have unearthed a lot of material during their excavation, so it was interesting to think of this tribe resettling this area doing the exact same thing we were- digging in the dirt and unearthing our shared human past.
tl;dr
Anyway, I digress. The moral of the story is, if you were to pick a good spot like the one we worked in, where there are plentiful resources, odds are it will have attracted more than one group over time. It is likely that if you pick such a spot, you might find one group at your earlier date, and a completely different, unrelated group there a thousand years later. We only know these cultures by the material evidence they left behind, but I can tell you at least from their pottery and other decorative items that they'd definitely be distinct if you looked at them side by side. They might not be significantly more or less advanced, per se, but they'd very likely be different and distinct. Anyone with even a fairly basic training in archaeology, like I had with a few classes and some hands-on experience, could probably identify which was which, but even a complete layperson would see that they were different.
Yes, the simplest way to see the difference is to look at what crops the native peoples are cultivating. In 50CE you would expect to see the Eastern Agricultural Complex making up the bulk of the diet of the natives. B y 1050 CE Maize is much more widely cultivated and the other two members of the "Three Sisters" will make up the bulk of their crops.
I have a question. How different would Denmark be between AD50 and AD1050?
Like suppose were in a small rural town or area of the country. What would the major changes I would see over that time?
I think you could depending on your what knowledge you're armed with. This site gives evidence of ceramic fragments around 50 AD. Here's another link New Jersey during the Late Woodland period (1000-1600 AD) which also evidences ceramic traditions. I supposed if you were familiar with ceramic evolution in the region, it may be rather easy to spot. The latter article suggests concentrated populations of indigenous New Jersey-ites appeared during Late Woodland and are the present day sites of modern cities like Trenton.
Here's another article on the Early/Middle Woodland period in New Jersey lasting from 1000BC-1000AD.
While there will be some similarities across time and space, what differences you notice will depend on where in New Jersey you are. I had some difficulty finding information about New Jersey specifically, so I hope you won't mind me expanding this discussion out a bit to include a larger region Mid-Atlantic region.
In 50 AD, you've just crossed over the Early-to-Middle Woodland divide for the the region. Coastal settlements are getting smaller and more seasonal, while inland settlements along the rivers and streams are getting larger and more permanent. Trade routes link the southern portion of the region to the dominant powers in the Ohio Valley, which have spread their influence over most of Delmarva to the south. The Delmarva Adena have some limited influence over southern New Jersey, but by 50 AD they're experiencing a cultural shift resulting in the Carey Complex in the region. Ceramics tend to be clay tempered and thick-walled. As others have mentioned, the bow was either absent or little used in the region at this time and the weapon of choice for hunting would have been the atlatl. Some components of the Eastern Agricultural Complex, such as a local species of amaranth and goosefoot, made it over the mountains and were employed in the Mid-Atlantic, but for the most part, people made use of the bounty of the sea, rivers, and forest, and appear to have been quite successful at it. Shellfish, fish, deer, and wild plants--especially nuts like hickory--are eaten in addition to cultivated plants. This seems to have been a successful subsistence strategy, as the population--based on the number and size of sites--is steadily increasing at this time. Within these communities, you would see some form of distinct social hierarchy, though it likely isn't hereditary. However, some men and women who have accumulated power, prestige, or wealth during their lives will be buried with tokens of that privileged place in society, including exotic goods from distant lands. This would be less noticeable in New Jersey itself than in Delmarva, though.
In 1050 AD, the situation is quite different. A major cultural shift took place in the 7th Century. This is likely the result of the Eastern Algonquian-speakers moving into the area from the north. When you arrive in the middle of the 11th Century, Algonquian-languages will now be dominant through most of the region, though you'd still find some pockets of Iroquoian and Siouan speakers, especially closer to the mountains. Shell-tempered ceramics with thinner walls than their predecessors are common, but its not the only way of making pottery in the region. Maize is creeping into the area from all sides. It is being spread by the Mississippians in the Southeast, through Virginia, and by the Iroquoians in the Northeast along the Susquehanna and the Hudson Rivers. While it catches on around the Chesapeake Bay, its still uncommon in most of New Jersey at this time. Settlements are once again becoming concentrated along major rivers--the Susquehanna and Potomac in particular. Here communities were growing into large, pallisaded towns. The Delaware Valley became increasingly populated as well, but the sites are more dispersed and the people there saw less need to fortify. The atlatls you saw before have given away to bows with small triangular points. The trade networks, that brought exotic goods to the coast from much further inland, were disrupted for a time but will be flowing again by 1050 AD. Copper, always a popular item, is one of, if not the most, common exotic item coming into the region. However, unlikely your previous visit, exotic goods are now more equitably distributed through most communities. You'll different sorts of funerals throughout the region. Some people are still building burial mounds, others bury their dead beneath their homes, others have large community cemeteries, and others employ ossuary reburials. Those last two will become increasingly common later in history.
Some sources and suggested reading for you, if you want to know more:
"Lenape" seems more or less a catch-all for any indigenous people between the area west of the Hudson & all the way through DE & MD. So its hard to tell where the cultural ties & development were overlooked, or where they didn't exist as the result of a congruent cultural which spanned x hundred miles. For instance, my hometown used to be a Lenape settlement in central Jersey. But nobody has any archaeological sites or other primary sources of information.
We do have evidence of Native American history changing over time, though - the way the Algonquin of Pennsylvania were forced north by the Iroquois of New York, for instance. Or the South Western 'cliff cities' which fell to water & timber scarcity. These occurred before or during the times of initial settlement.
Tl;Dr: excellent & important question precisely because we the answer is so hidden.
But, in general, yes - Native American culture adapted & eveolved through time prior to European intervention.